It would be useful to know why you wish to transfer your family tree to Ancestry as there may be alternatives.

Unfortunately it is not a simple process for several reasons.
Firstly, you need to consider the privacy of sensitive data of living people that should not be published online.
Secondly, Ancestry does not support standard GEDCOM very well and certainly not the FH GEDCOM extensions.

In summary the steps involve:

Use File > Import/Export > Export > GEDCOM File to choose who to include and create a GEDCOM to manipulate

Thanks Mike. My DNA and an old family tree are on Ancestry so I would like to update this. I have had major problems in the past doing so (messages files not recognised by Ancestry, etc) and as aged computer novice, I was wondering if a a step by step guide to be available on the FHUG. Not sure I understand the plugin but will look further into this. Thanks. Richard

You won't be able to update the existing Ancestry tree, but will have to create a new one.
If you had tried uploading the FH GEDCOM file directly from your Project, then Ancestry would not recognise that.

After having reviewed the advice, if you need specific advice then please ask.